The San Diego Union-Tribune reports that as of September, more than 30 schools in the 132,000-student district had no air-conditioned classrooms; 47 schools had less than half of their classrooms air-conditioned; and 119 schools had air conditioning in at more than half of their classrooms.

Capital funding for the upgrades will come from bond funds approved by voters in 2008 and 2012.

Beyond costs of construction, the district estimates that the added air conditioning will increase the system's energy expenditures by $2.8 million a year. To offset those costs, San Diego plans a $40 million project to install solar panels at 16 to 20 schools in 2016 and 2017.

The decision to install air conditioning in all classrooms comes less than three years after the board voted to bring air conditioning to 2,000 of the district's hottest classrooms. That work is substantially complete, board documents say.